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EPEG 413

EPEG 413                              POWER SYSTEMS II                                                    3 Credits

Objective: To gain a broad understanding of the performance of modern power systems and the analysis and computation of large three phase systems.


General Background: Growth of electric power system, energy production; Transmission and distribution; Load studies, economic load dispatch, fault calculations; System protection, stability studies; Power system engineering.

Introduction: Single and double subscript notation, power in single-phase AC circuits; Complex power triangle, direction of power flow; Voltage and current in balanced three phase circuits; Power in balanced three phase circuits; Per unit quantities.

System Modelling: Construction of synchronous machine; Armature reaction and circuit model in a synchronous machine; Effect of synchronous machine excitation; Ideal transformer, equivalent circuit of practical transformer; Autotransformer, PU impedance in 1-phase transformer circuits, 3-phase transformer; PU impedance of 3 winding transformer; One line diagram, impedance and reactance diagram; Advantages of PU computing.

Load-Flow Solutions and Control: Data for load- flow studies; Gauss-Seidel method, Newton - Raphson method; Digital - computer studies of load flow; Information obtained in a load flow study, numerical results; Control of power into a network; Specification of bus; Voltage, capacitor banks, control by transformer; Optimal load flow solution

Symmetrical Three Phase Faults: Transients in RL series circuits; Short - circuit currents and the reactances of synchronous machines; Internal voltages of loaded machines under transient condition; Bus impedance matrix in fault calculations; Bus impedance matrix equivalent networks; Selection of circuit breakers

Symmetrical Components: Synthesis of asymmetrical phasors from their symmetrical components; Symmetrical components of asymmetrical phasors; Phase shift of symmetrical components in Y-Delta transformer banks; Power in terms of symmetrical components; Unsymmetrical series impedances, sequence impedances and sequence networks; Sequence networks of unloaded generators, sequence impedance -positive and negative sequence networks, zero sequence networks.

Unsymmetrical Faults: Single line to ground fault on an unloaded generator; Line to line fault on an unloaded generator; Double line to ground fault of an unloaded generator, Unsymmetrical faults on power systems; Single line to ground fault on power system; Line to line fault on power system; Double line to ground fault on a power system; Interpretation of the interconnected sequence networks; Analysis of unsymmetrical faults using the bus impedance matrix; Fault through impedance, computer calculations of fault currents

Power System Stability: Stability problem, rotor dynamics and the swing equation; Power angle equation, synchronising power coefficients; Equal area criterion of stability, further applications of the equal area criterion; Multi-machine stability studies- classical representation; Step by step solution of the swing curve; Transient stability studies, factor affecting transient stability.


  1. W D Stevenson, Elements of Power System Analysis, 4th Ed., TMH 1982
  2. C A Groues, Power System Analysis, Wiley NY 1986

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